OIL FILTER COMPRISING A HYDRAULIC RESISTANCE

Abstract

The present invention relates to an oil filtration unit (1) for removal of solid contaminants from contaminated oil, the oil filtration unit (1) comprising a housing (2) which comprises a housing inlet (3) adapted to receive contaminated oil from the surroundings and to release the contaminated oil to an inner opening (4) of the housing (2) at a first pressure (p1) and a housing outlet (12) adapted to release filtered oil to the surroundings, and an oil filter (6) for filtering the contaminated oil, the oil filter (6) being arranged in the inner opening (4) of the housing (2) and comprising a filter inlet defined by an outer surface (7) of the oil filter (6), an inner filter volume (8) adapted to receive filtered oil at a second pressure (p2), where the second pressure (p2) is lower than the first pressure (p1), and a filter outlet inside the housing (2) providing fluid/liquid communication between the inner filter volume (8) and the housing outlet (12) in order to release the filtered oil from the inner filter volume (8), where the filter outlet comprises a hydraulic resistance providing a fluid/liquid flow restriction between the inner filter volume (8) and the housing outlet (12) in order to increase the second pressure (p2) inside the inner filter volume (8) and to release the filtered oil from the inner filter volume (8) to the housing outlet (12) at a third pressure (p3), where the third pressure (p3) is lower than the second pressure (p2).

Claims

1. Oil filtration unit (1) for removal of solid contaminants from contaminated oil, the oil filtration unit (1) comprising: a housing (2) which comprises a housing inlet (3) adapted to receive contaminated oil from the surroundings and to release the contaminated oil to an inner opening (4) of the housing (2) at a first pressure (p1) and a housing outlet (12) adapted to release filtered oil to the surroundings, and an oil filter (6) for filtering the contaminated oil, the oil filter (6) being arranged in the inner opening (4) of the housing (2) and comprising a filter inlet defined by an outer surface (7) of the oil filter (6), an inner filter volume (8) adapted to receive filtered oil at a second pressure (p2), where the second pressure (p2) is lower than the first pressure (p1), and a filter outlet inside the housing (2) providing fluid/liquid communication between the inner filter volume (8) and the housing outlet (12) in order to release the filtered oil from the inner filter volume (8), characterised in that the filter outlet comprises a hydraulic resistance forming part of the oil filter, said hydraulic resistance providing a fluid/liquid flow restriction between the inner filter volume (8) and the housing outlet (12) in order to increase the second pressure (p2) inside the inner filter volume (8) and to release the filtered oil from the inner filter volume (8) to the housing outlet (12) at a third pressure (p3), where the third pressure (p3) is lower than the second pressure (p2).

2. Oil filtration unit (1) according to claim 1, characterised in that the oil filtration unit (1) is suitable for removal of solid contaminants from air-containing, contaminated oil.

3. Oil filtration unit (1) according to claim 1, characterised in that the filter outlet comprises natural or synthetic polymer.

4. Oil filtration unit (1) according to claim 1, characterised in that an end plate of the oil filter (6) comprises the filter outlet.

5. Oil filtration unit (1) according to claim 1, characterised in that the hydraulic resistance comprises a valve device, a porous material or an orifice arrangement.

6. Oil filtration unit (1) according to claim 5, characterised in that the porous material and/or the orifice arrangement comprises natural or synthetic polymer.

7. Oil filtration unit (1) according to claim 5, characterised in that the orifice arrangement comprises one or more holes (20;25;26;27).

8. Oil filtration unit (1) according to claim 7, characterised in that the one or more holes (20;25;26) of the orifice arrangement are through-going.

9. Oil filtration unit (1) according to claim 7, characterised in that the one or more holes (27) of the orifice arrangement are blind.

10. Oil filtration unit (1) according to claim 7, characterised in that the orifice arrangement comprises 1, 3, 8, 10, 15, 20, 25, 30, 40 or 50 holes (20;25;26;27).

11. Oil filtration unit (1) according to claim 4, characterised in that an outer surface of the end plate of the oil filter (6) comprises grooves (22,23) extending in a direction orthogonally and/or radially to a longitudinal axis of said end plate.

12. Oil filtration unit (1) according to claim 11, characterised in that the orifice arrangement comprises one or more holes (20;25;26;27) and characterised in that the holes (20;25;26;27) of the orifice arrangement are arranged at one or more of the grooves (22,23) of the end plate of the oil filter (6).

13. An oil filter (6) for removal of solid contaminants from contaminated oil, the oil filter (6) comprising a filter inlet defined by an outer surface (7) of the oil filter (6) adapted to receive the contaminated oil at a first pressure (p1), an inner filter volume (8) adapted to receive filtered oil at a second pressure (p2) being lower than the first pressure (p1), and a filter outlet providing fluid/liquid communication between the inner filter volume (8) and the surroundings in order to release the filtered oil from the inner filter volume (8) characterised in that the filter outlet comprises a hydraulic resistance forming part of the oil filter, said hydraulic resistance providing a fluid/liquid flow restriction between the inner filter volume (8) and the surroundings in order to increase the second pressure (p2) inside the inner filter volume (8) and to release the filtered oil from the inner filter volume (8) at a third pressure (p3), where the third pressure (p3) is lower than the second pressure (p2).

14. A method for removal of solid contaminants from contaminated oil, the method comprising the steps of providing an oil filtration unit (1) comprising a housing (2) which comprises a housing inlet (3) and a housing outlet (12), providing an oil filter (6) in an inner opening (4) of the housing (2), the oil filter (6) comprising a filter inlet defined by an outer surface (7) of the oil filter (6) and a filter outlet, introducing contaminated oil from the surroundings via the housing inlet (3) into the inner opening (4) of the housing (2) at a first pressure (p1) so that the contaminated oil is exposed to the filter inlet and is divided, when passing the oil filter (6), into solid contaminants retained by the oil filter (6) and filtered oil released into an inner filter volume (8) at a second pressure (p2), where the second pressure (p2) is lower than the first pressure (p1), and releasing the filtered oil from the inner filter volume (8) via the filter outlet providing fluid/liquid communication between the inner filter volume (8) and the housing outlet (12), characterised in that a hydraulic resistance providing a fluid/liquid flow restriction between the inner filter volume (8) and the housing outlet (12) and forming part of the oil filter is provided at the filter outlet in order to increase the second pressure (p2) inside the inner filter volume (8) and to release the filtered oil from the inner filter volume (8) to the housing outlet (12) at a third pressure (p3), where the third pressure (p3) is lower than the second pressure (p2).

15. A method according to claim 14, characterised in that the method is suitable for removal of solid contaminants from air-containing, contaminated oil.

16. Oil filtration unit (1) according to claim 8, characterised in that the orifice arrangement comprises 1, 3, 8, 10, 15, 20, 25, 30, 40 or 50 holes (20;25;26;27).

17. Oil filtration unit (1) according to claim 9, characterised in that the orifice arrangement comprises 1, 3, 8, 10, 15, 20, 25, 30, 40 or 50 holes (20;25;26;27).

18. Oil filtration unit (1) according to claim 12, characterised in that the one or more holes (20;25;26) of the orifice arrangement are through-going.

19. Oil filtration unit (1) according to claim 12, characterised in that the one or more holes (27) of the orifice arrangement are blind.

20. Oil filtration unit (1) according to claim 12, characterised in that the orifice arrangement comprises 1, 3, 8, 10, 15, 20, 25, 30, 40 or 50 holes (20;25;26;27).

Description

[0075] The structure and function of the oil filtration unit and the method of using it will be described in more detail below with references to exemplary embodiments shown in the drawings wherein,

[0076] FIG. 1 shows an embodiment of a cross section of an oil filtration unit comprising an oil filter, seen from the side.

[0077] FIG. 2 shows an embodiment of an oil filter comprising a hydraulic resistance, seen from the side.

[0078] FIG. 3 shows an embodiment of a cross section of the oil filter of FIG. 2, seen along the longitudinal axis of the oil filter.

[0079] FIG. 4 shows an embodiment of a perspective view of an oil filter comprising a hydraulic resistance.

[0080] FIG. 5 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate.

[0081] FIG. 6 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate.

[0082] FIG. 7 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate.

[0083] FIG. 8 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate.

[0084] FIG. 9 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate.

[0085] In the figures, the oil filter is shown describing having a cylindrical shape. However, it should be understood that other shapes of oil filters are also intended within the scope of the present invention.

[0086] FIG. 1 shows an embodiment of a cross section of an oil filtration unit comprising a housing and an oil filter, seen from the side.

[0087] The oil filtration unit 1 may comprise a housing 2 which comprises a housing inlet 3 adapted to receive contaminated oil from the surroundings and feeding the oil at a first pressure p1 to an inner opening 4 of the housing 2 of the oil filtration unit 1 as illustrated by the arrow 5.

[0088] The oil filtration unit 1 may comprise an oil filter 6 for filtering the contaminated oil, the oil filter 6 being arranged in the inner opening 4 of the housing 2. The oil filter 6 may comprise an outer surface 7 defining a filter inlet and an inner filter volume 8 adapted to receive filtered oil at a second pressure p2. The second pressure p2 may be lower than the first pressure p1. Furthermore, the oil filter 6 may comprise a filter outlet inside the housing 2 providing fluid/liquid communication between the inner filter volume 8 and the surroundings of the oil filter 6, and the filter outlet may thus be adapted to release the filtered oil from the inner filter volume 8, where the filter outlet may be arranged at an end plate 9 of the oil filter 6.

[0089] A sealing 10 may be arranged between the end plate 9 of the oil filter 6 and an inner end surface 11 of the housing 2, as is illustrated in FIG. 1. The sealing 10 may comprise an elevation. The elevation may form a closed path and may form a circle on the inner end surface 11 of the housing 2. Thus, when the oil filter 6 is inserted into the inner opening 4 of the housing 2, the elevation may come into contact with the end plate 9 of the oil filter 6 and protrude or cut into the oil filter 6. Thus, sealing is provided between the housing 2 and the oil filter 6 resulting in the oil to be filtered being prevented from flowing directly from the housing inlet 3 to a housing outlet 12 and thus from bypassing the oil filter 6.

[0090] Instead, contaminated oil, which has been introduced into the inner opening 4 of the housing 2 and been exposed to the outer surface 7, i.e. filter inlet, of the oil filter 6, may flow through the filter inlet. During passage of the oil filter 6, as indicated by the arrows 13, the contaminated oil may be divided into solid contaminants retained by the oil filter 6 and filtered oil released into the inner filter volume 8 at a second pressure p2 being lower than the first pressure p1 due to the flow resistance through of the oil filter 6.

[0091] The filtered oil may be released from the inner filter volume 8 to the surroundings via firstly the end plate 9 comprising the filter outlet and secondly via the housing outlet 12 of the oil filtration unit 1, as illustrated by the arrow. The filter outlet may comprise a hydraulic resistance providing a fluid/liquid flow restriction between the inner filter volume 8 and the housing outlet 12 in order to increase the second pressure (p2) inside the inner filter volume 8. The hydraulic resistance results in the filtered oil being released from the inner filter volume 8 at a third pressure p3 being lower than the second pressure p2. As a consequence of a hydraulic resistance at the filter outlet, the second pressure p2 in the inner filter volume 8 is larger than would be the case if no hydraulic resistance was present at the filter outlet. Thus, a back pressure is provided which ensures that air in the oil remains dissolved and does not affect the filtration efficiency.

[0092] FIG. 2 shows an embodiment of an oil filter comprising a hydraulic resistance, seen from the side. For similar features, similar reference numbers have been used.

[0093] The oil filter 6 may have a substantially cylindrical shape and consist of several plates and inter alia a first 14 and a second end plate 15 and one or more centre plates 16, where the first 14 and second end plate 15 may each comprise an outer end surface 17,18, respectively. Furthermore, the oil filter 6 may comprise at least one side surface 19, where at least part of said outer end surfaces 17,18 and said at least one side surface 19 constitute the filter inlet.

[0094] In the embodiment of FIG. 2, the side surface 19 is illustrated as being uneven and comprising e.g. several grooves, but other shapes of the side surface 19, such as an even side surface 7, are foreseen within the present invention. Furthermore, it is foreseen within the present invention that the oil filter 6 may e.g. be produced in one uniform piece instead of from several plates.

[0095] The oil filter 6 may comprise a longitudinal axis A. The oil filter 6 and/or the end plate 14 of the oil filter 6 may comprise natural or synthetic polymer and may comprise a cellulose material.

[0096] FIG. 3 shows an embodiment of a cross section of the oil filter 6 of FIG. 2, seen along the longitudinal axis A of the oil filter 6. For similar features, similar reference numbers have been used.

[0097] The oil filter 6 may comprise an inner filter volume 8 for receiving filtered oil, which has been filtered from solid contaminants retained in the filter material, when the contaminated oil moves from the inner opening 4 of the housing 2 to the inner filter volume 8.

[0098] The oil filter 6 may comprise a filter outlet comprising a hydraulic resistance adapted to release the filtered oil from the inner filter volume 8 at a third pressure p3. In FIG. 3, the first end plate 14 of the oil filter 6 is illustrated as comprising a filter outlet in the form of an orifice arrangement comprising one through-going hole 20 with a cross section being smaller than the cross section of the inner filter volume 8. However, within the present invention it is understood that other types of the hydraulic resistances are foreseen and may e.g. comprise a porous material or a valve device such as a check valve or nonreturn valve.

[0099] The size of the hydraulic resistance, which may comprise the valve device, the porous material or the orifice arrangement, depend on a number of factors such as the temperature, the viscosity of the oil, the flow of the oil through oil filter, the total cross sectional area of the holes and pores in the filter outlet and the size of the holes and pores.

[0100] In case the first end plate 14 in FIG. 3 comprises a porous material through which the oil may flow, at least part of the first end plate 14 may also form part of the filter outlet.

[0101] FIG. 4 shows an embodiment of a perspective view of an oil filter comprising a hydraulic resistance. For similar features, similar reference numbers have been used as in the previous Figs.

[0102] The oil filter 6 is shown as comprising a first end plate 14 comprising an outer end surface 17. The first end plate 14 may comprise a hydraulic resistance in the form of an orifice arrangement comprising one through-going hole 20.

[0103] The outer end surface 17 may comprise one or more substantially linear ridges 21 and grooves 22 which may be arranged adjacent to each other. The linear ridges 21 and grooves 22 may extend orthogonally to the longitudinal axis A of the oil filter 6. A circular groove 23 may surround the linear ridges 21 and grooves 22 and may as such extend circularly around the longitudinal axis A of the oil filter 6 with a constant radius. The circular groove 23 and the linear grooves 22 may be level with each other. The ridges 21 may be level with a part 24 of the outer end surface 17 at the periphery 14 of the end plate 14 which is illustrated as being planar in FIG. 4. Said linear grooves 22 may be mutually connected via the circular groove 23. However, it is foreseen that said linear grooves 22 may also be mutually connected themselves. Furthermore, it is foreseen that the linear grooves 22 may be non-linear, such as curved or extend in zigzags.

[0104] The through-going hole 20 may protrude the outer end surface 17 of the first end plate 14 in one of said linear 22 or circular grooves 23 and is illustrated in FIG. 4 as being positioned in one of the linear grooves 22 and may extend substantially linearly with the longitudinal axis A of the oil filter 6.

[0105] When the oil filter 6 has been inserted into the inner opening 4 of the housing 2, at least one of the outer end surfaces 17,18 may come into contact with an inner end surface of the housing 2. Thus, the outer end surface 17 of the first end plate 14 may come into contact with the inner end surface 11 of the housing 2, and as the ridges 21 may be level with the part 24 of the outer end surface 17 at the periphery 14 of the first end plate 14, the ridges 21 and said part 24 of the outer end surface 17 may come into contact with the inner end surface 11 of the housing 2. Thus, the ridges 21 may rest on said inner end surface 11 and provide support for the first end plate 14 on the inner end surface 11 which may be advantageous in order to prevent/minimise mechanical deformation of the first end plate 14 due to the difference in pressure between before (i.e. p2) and after (i.e. p3) the filter outlet.

[0106] As said linear 22 and circular grooves 23 may be mutually connected, said linear 22 and circular grooves 23 may distribute the filtered oil, which has been released from the inner filter volume 8, so that the filtered oil may flow freely and be released through the housing outlet 12 to the surroundings.

[0107] FIG. 5 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate. For similar features, similar reference numbers have been used.

[0108] In the embodiment of FIG. 5, the first end plate 14 is illustrated as comprising at least three through-going holes 25 each extending from an inner end surface 17 towards the outer end surface 17 and protruding the outer end surface 17 in one of the linear grooves 22. The three through-going holes 25 may have a substantially similar size, i.e. a similar length, width and cross-sectional area.

[0109] The at least three through-going holes 25 may each be tubular with a constant radius, such as cylindrical, and/or with a constant cross-sectional area, such as a square cross section, and may be mutually parallel.

[0110] FIG. 6 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate. For similar features, similar reference numbers have been used.

[0111] In the embodiment of FIG. 6, the first end plate 14 is illustrated as comprising at least seven through-going holes 25 each extending from an inner end surface 17 towards the outer end surface 17, and six of which each protrudes the outer end surface 17 in one of the linear grooves 22, and one of which protrudes the outer end surface 17 in the circular groove 23. The seven through-going holes 25 may have a substantially similar size, i.e. a similar length, width and cross-sectional area.

[0112] The at least seven through-going holes 25 may each be tubular with a constant radius, such as cylindrical, and/or with a constant cross-sectional area, such as a square cross section, and may be mutually parallel.

[0113] FIG. 7 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate. For similar features, similar reference numbers have been used.

[0114] In the embodiment of FIG. 7, the first end plate 14 is illustrated as comprising at least seven through-going holes 26 each extending from an inner end surface 17 towards the outer end surface 17, and six of which each protrudes the outer end surface 17 in a linear groove 22, and one of which protrudes the outer end surface 17 in the circular groove 23. The seven through-going holes 25 may have a substantially similar size, i.e.

[0115] a similar length, width and cross-sectional area.

[0116] The at least seven through-going holes 26 may each be tubular with a radius varying along their length, such as frustoconical, and/or with a non-circular cross-sectional area, such as a square cross section. The radius and/or cross-sectional area may be largest downstream of the filter outlet.

[0117] Thus, as said holes 25,26 may be through-going, the first end plate 14 may comprise a non-porous material, such as e.g. a plastic or metallic material, or may comprise a porous material, such as natural or synthetic material, through which the filtered oil may move so that the first end plate 14 may form a part of the filter outlet. The material of the first end plate 14 may be chosen depending on the wanted back pressure.

[0118] FIG. 8 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate. For similar features, similar reference numbers have been used.

[0119] In the embodiment of FIG. 8, the first end plate 14 is illustrated as comprising at least seven blind holes 27, six of which each extends from a linear groove 22 towards the inner end surface 17 of the end plate 14, and one of which extends from the circular groove 23 towards the inner end surface 17. The seven blind holes 27 may have a substantially similar size, i.e. a similar length, width and cross-sectional area.

[0120] The at least seven blind holes 27 may each be tubular with a constant radius, such as cylindrical, and/or may have a non-circular cross-section, such as a square cross section, and/or may be mutually parallel. However, it is foreseen that the at least seven blind holes 27 may also have a varying radius or cross-sectional area along their length.

[0121] Thus, in the embodiment of FIG. 8, the filtered oil may be released from the inner filter volume 8 by moving through the material of the first end plate 14 starting from the inner end surface 17 of the first end plate 14 and may flow through the at least seven blind holes 27 the remaining distance to the outer end surface 17 of the first end plate 14 when reaching said blind holes 27 in the first end plate 14. Thus, the first end plate 14 may comprise a porous material and may comprise natural or synthetic polymer so as to facilitate the movement of the filtered oil through the first end plate 14.

[0122] It is foreseen that the through-going holes 25,26 and/or blind holes 27 may have varying sizes and the number may vary. However, advantageously, there is a symmetry in the size of said holes 25,26,27 relative to the longitudinal axis A of the oil filter and thus of the longitudinal axis of the first end plate 14 such that the pressure and mechanical stress on the first end plate 14 is evenly distributed on the first end plate 14.

[0123] Letting said holes 25,26,27 protrude in the linear 22 and/or circular grooves 23 facilitates that the filtered oil is evenly distributed across the first end plate 14 after being released from the inner filter volume 8.

[0124] For example, in the case where the end plate 14 comprises three holes 25,26,27, said three holes 25,26,27 may be arranged in the three linear grooves 22 closest to the longitudinal axis of the end plate 14, or one in the linear groove 22 closest to said longitudinal axis and two in the linear grooves 22 third-closest to said longitudinal axis.

[0125] FIG. 9 shows an embodiment of a cross section of an end plate, seen along the longitudinal axis of the end plate. For similar features, similar reference numbers have been used.

[0126] In the embodiment of FIG. 9, the first end plate 14 is illustrated as not comprising any holes 25,26,27. Thus, in order for the filtered oil to be released from the inner filter volume 8, the first end plate 14 may comprise a porous material so as to facilitate the movement of the filtered oil through the pores of the first end plate 14. The first end plate 14 may at least partly comprise a natural or synthetic material so that the first end plate 14 may participate in filtering the oil.

[0127] It is foreseen that the hydraulic resistance may comprise at least one valve device, such as a back pressure valve, which may be a check valve or a non-return valve, and the valve device may be spring loaded. The number of valve devices and the cracking pressure, i.e. the inlet pressure at which the first indication of flow occurs, may be determined depending of the desired back pressure.

[0128] Therefore, the filter outlet may comprise various features and have various shapes depending on e.g. the viscosity of the filtered oil, the type of oil, the flow, specific operational conditions, the desired back pressure, the air content in the oil etc.

[0129] Modifications and combinations of the above principles and designs are foreseen within the scope of the present invention.